Stinky tofu is a special fermented food product found in Taiwan, amongst other places. Stinky tofu is considered by many Chinese to be a particularly flavorful and delicious dish. The conventional stinky tofu is produced through an open fermentation process which comprises curing ingredients such as vegetables and shrimp etc. by salt in the natural environment; allowing the putrefaction of the ingredients, and thus obtain a stinky brine (the aromatic fermentation liquid for stinky tofu); immersing and fermenting tofu (ie. soybean curd) in the stinky brine for 4-6 hours; and recovering said tofu from brine (Su, Y. C. Traditional fermented foods in Taiwan, In Proceedings of the Oriental Fermented Foods, p.15, Food Industry Research and development Institute, Taiwan, Hsinchu, 1980). The fermented stinky tofu, usually cut into squares, is then cooked prior to consumption.
Stinky tofu is obtained by an alkaline fermentation. During the fermentation process, microorganisms are able to hydrolyze proteins to amino acids and peptides, accompanied by the release of ammonia and a subsequent increase of pH of the fermenting mixture. The main microorganism responsible for the alkaline fermentation are Bacillus sp. Most of the microorganisms are capable of secreting extracellular enzymes to hydrolyze proteins to amino acids and peptides and release ammonia during the fermentation (Wang, J. and Fung, D. Y. C., Alkaline-fermented foods: a review with emphasis on pidan fermentation. Crit. Rev. Microbial. 22:101, 1996).
The strains of microorganisms conventionally used for fermentation of stinky tofu are mainly from the stinky brine, which is inoculated by chance from the environment and ingredients. Therefore, the quality, and consistency of product is not predictable; for example, the flavor of the product is varied depending on each batch of the brine, even if the brine is made comprising the same ingredients. In addition, in the conventional production of stinky brine, the ingredients are only roughly cut, then mixed, and thus not easily degraded by the microorganisms. Thus, the growth of the microorganisms is slow. In general, it takes more than six months to complete the fermentation process to produce stinky brine. Owing to the conventional use of open fermentation, the odor produced in the fermentation attracts insects, which then gather and lay eggs in the fermenting mixture. Thus, using conventional methods sanitation is very poor. A variety of pathogenic fungal infectious agents harmful to human health could also easily contaminate the fermenting mixture. Thus, it would be most useful to develop a sanitary method for producing uncooked stinky tofu, that is repeatable and produces consistent quality of product, as well as allows for improved food safety and product handling.